Re: SpectraFix = casein?
In regards to the changing and darkening of soft pastels when fixatives are used, some of the fault lies in how strong and penetrating the resins within the fixatives are, how heavily they are applied, etc.; but a fair amount of blame for color shifts can be blamed on the amount of fillers and chalk that is used by the manufacturer of the pastel sticks.
If a light blue pastel stick is made from Ultramarine Blue pigment and made into tints by the addition of chalk (which is often the case with student grade pastels), when the blue tint is sprayed with any fixative, no matter how excellent the quality of the fixative is, the chalk portion of the mark will largely disappear even after the fixative is fully dry and the color of the blue could shift from a light tint to something closer to the color of a thin layer of ultramarine blue oil paint. If instead of chalk, the manufacturer used Titanium White to mix with the Ultramarine Blue, the marks made by that pastel stick will change little at all under a light layer of fixative.
Soft pastels are not supposed to be smear-proof after being fixed. It can be used to isolate different layers of the painting from intermixing unintentionally, and to reduce the migration of dust within the frame. Using too much fixative, no matter how carefully applied, will alter the manner that the light rays refract off the pastel's surface. Loose dust should be knocked off the painting prior to fixing, then spray the lightest coat possible and do not spray so much on that it appears damp.
I consigned a batch of pastels to a gallery who then framed the pieces. Without my permission, they used so much fixative that I didn't recognize my own work. The entire surface was shiny rather than velvety matt. I successfully sued for the entire consignment price and was able to keep the ruined work to prevent my work from being sold or displayed in a manner I would never endorse. It is up to each artist to choose whether or not they wish to use fixatives, or under what circumstances they wish to use them, but in my personal opinion, if so much fixative is used that the velvety matt surface is no longer just that, the artist has changed the medium from soft pastel to something else entirely.
I do like Spectrafix, and even though they claim little or no color shift, I notice some. If the mist should include larger droplets that are visible after it dries, or if I didn't get out of the rain in time, all you need to do to repair the dark spots is to wait until the painting is entirely dry, then agitate that spot lightly and the dark spot will disappear. I also like Spectrafix because it can be used safely indoors without fancy ventilation or in a classroom setting.
Last edited by el Tea : 06-20-2011 at 12:55 AM.
Reason: clarification of meaning